1. Field of the Invention
The present invention generally relates to electroplating of a metal film on a substrate. More particularly, the present invention relates to containing a processing fluid to selected areas within an electroplating system.
2. Background of the Related Art
A variety of processes are performed on semiconductor substrates, such as semiconductor wafers, LCD displays, etc. During such processing, it is desired to keep the substrate as clean as possible. There are a variety of wet processes, such as electroplating, in which the substrate is immersed in a fluid such as electrolyte solution. During electroplating, it becomes especially challenging to keep the substrate clean since the processing involves the immersion of the substrate into electrolyte solution. Electroplating is performed by applying a prescribed voltage across an electrolyte solution between the seed layer on the substrate and an anode. Electroplating deposits metal ions contained within the electrolyte solution on the layer to form the deposited metal film. Electroplating is a wet process in which a fluid electrolyte solution suspends, and transports, metal ions, such as copper sulfate. A metal film is deposited on the seed layer when sufficient negative voltage, known as plating voltage, is applied between the seed layer and the anode. Immersing the substrate into a liquid such as electrolyte solution makes keeping the substrate clean from impurities very difficult.
The use of electroplating in integrated circuit design originated with the fabrication of lines on circuit boards. Electroplating is now used to deposit metals, such as copper, on substrates to form features, such as vias, trenches, or contacts. One embodiment of feature filling technique that includes electroplating requires initially depositing a diffusion barrier layer on the substrate using physical vapor deposition (PVD) or chemical vapor deposition (CVD). A seed layer is then deposited on the diffusion barrier layer using PVD or CVD to define a plating surface. A metal film is deposited on the seed layer on the substrate by electroplating. Finally, the deposited metal film can be planarized by another process, e.g., chemical mechanical polishing (CMP).
There are a variety of depositions, chemicals, etc that form on certain locations on substrates, as a result of electroplating, that are desired to remove. For example, undesired deposits formed from the plating material (such as copper) typically form on the backside and/or edge of the substrate surface. Spin-rinse-dry (SRD) and integrated bevel clean (IBC) systems are often used following electroplating to remove the undesired deposits primarily respectively on the backside and on the edge of the substrate. SRD systems and IBC systems both involve the application of wet etchants to the substrate to remove the undesired deposits on the substrate. De-ionized water is applied to the substrate surfaces in the SRD and IBC systems to rinse the etchant from the surface of the substrate.
Crystals are another undesired substance that forms on substrates. A chemical containing a metal, such as copper sulfate, is contained within the electrolyte solution during processing. As the substrate is removed from the electrolyte solution, some copper sulfate crystals may remain on the substrate. As the electrolyte solution dries on the surface of the substrate, some impurities such as copper sulfate crystals are formed on a surface of the substrate (the front side, the backside, the edge, etc.). As the substrates are handled by robots, the copper sulfate crystals contact the robots, certain portions of subsequent process cells, and other system components. As further substrates are handled by the robots, or processed within the process cells, the latter substrates may also have contact with the crystals.
Therefore, there remains a need for system that limits the formation of crystal material, deposited material, etc. on selected areas of substrate surfaces during wet processes such as electroplating.
The present invention generally provides a wet processing system such as, for example, electroplating. More particularly, a method and apparatus for processing a substrate is described. In one aspect, a processing system is provided which includes a wet area and a dry area. In another aspect, a method comprises processing the substrate in the process cell. The substrate is transferred from the process cell to a dry module and then transferring the substrate to a drying area.